CALLISTEMON—Bottle-Brush Tree (Calliste’mon).
Tender evergreen flowering shrubs from Australia which belong to the Myrtle family, Myrtaceae. They are well adapted for growing outdoors in California and in similar mild climates and for greenhouse cultivation elsewhere. They have narrow, dark-green, leathery leaves, which are slightly aromatic when crushed. The flowers are densely packed in terminal cylindrical spikes resembling a bottle brush in shape and size, hence the common name. The name Callistemon is derived from the Greek kallos, beauty, and stem on, a stamen, and refers to the beautiful stamens. The stamens, which are brilliantly colored, protrude well beyond the petals and form the most conspicuous feature of the flower.
By hard annual pruning, these plants can be cultivated in 6 or 8-in. pots and in larger tubs, or they may be planted in a bed of soil in the conservatory where they will grow from 8-10 ft. in height.
Soil Compost and Pruning. When these shrubs are grown in a greenhouse, a minimum winter temperature of 45 degrees is required. The best compost consists of a rich, porous, peaty soil with sand added freely. Repotting is done in early spring as soon · as new growth begins, and the compost is rammed firmly with a potting stick. Pruning, which consists of shortening the vigor ous shoots by one half and the weaker ones by two thirds, is carried out as soon as the flowers have faded. Callistemons require full exposure to sunlight to develop the flower buds, for which purpose they may be plunged in ashes out of doors during the summer.
Sowing Seeds and Taking Cuttings. Propagation is effected by sowing seeds in pots of sandy peat in April, or by cuttings of firm shoots inserted in pots containing a similar compost and placed under a bell jar in the greenhouse in July or August. The rooted cuttings are potted in 3-in. pots and subsequently in larger ones. The main shoot of the young plant is cut back by half and the subsequent side branches are treated similarly to ensure a well-branched specimen.
The best kinds are Callistemon (Metrosideros) speciosus, crimson, April; C. lanceolatus, red, and var. splendens, scarlet, the best of all, June; and C. salignus, yellow or light pink, June.